Stephen Craik - Academia.edu (original) (raw)
Papers by Stephen Craik
BMJ Open
IntroductionThe COVID-19 pandemic has an excessive impact on residents in long-term care faciliti... more IntroductionThe COVID-19 pandemic has an excessive impact on residents in long-term care facilities (LTCF), causing high morbidity and mortality. Early detection of presymptomatic and asymptomatic COVID-19 cases supports the timely implementation of effective outbreak control measures but repetitive screening of residents and staff incurs costs and discomfort. Administration of vaccines is key to controlling the pandemic but the robustness and longevity of the antibody response, correlation of neutralising antibodies with commercial antibody assays, and the efficacy of current vaccines for emerging COVID-19 variants require further study. We propose to monitor SARS-CoV-2 in site-specific sewage as an early warning system for COVID-19 in LTCF and to study the immune response of the staff and residents in LTCF to COVID-19 vaccines.Methods and analysisThe study includes two parts: (1) detection and quantification of SARS-CoV-2 in LTCF site-specific sewage samples using a molecular assa...
Colloids and Surfaces B: Biointerfaces, 2019
Pilot-scale direct filtration challenge experiments were conducted to determine the impact of che... more Pilot-scale direct filtration challenge experiments were conducted to determine the impact of chemical pretreatment and filter design on the removal of Cryptosporidium surrogates dosed into the filter influent water at low temperatures (Average 0.5˚C). Copolymers-modified microspheres were identified as representative Cryptosporidium oocysts surrogates based on our previous findings and were used to evaluate the oocysts filtration removal at this pilot-scale study. The operational parameters examined included coagulant type (aluminum sulfate (alum) versus polyaluminium chloride (PACl)), filter aid polymer type (polyamine Magnafloc ® LT-7981 versus poly(Dimethyl Diallyl Ammonium Chloride) (polyDADMAC) Magnafloc ® LT-7995) and dose (0.5 versus 2.0 mg/L), and filter configuration (regular versus deep bed filters). The study found that higher Cryptosporidium surrogate removal was associated with higher polymer dose (2 mg/L) of polyDADMAC polymer and the deep bed filter configuration. The difference in surrogate removal between PACl and alum was no significant at cold temperature conditions tested. The deep bed filters were associated with higher surrogate removal, while exhibiting lower rates of flow reduction and longer filter run time. This work emphasizes the importance of optimizing chemical pretreatment and filter configuration for removing surrogates of Cryptosporidium oocysts in cold-water conditions in granular media water filtration processes. This pilot-scale study also demonstrated the exceed 2.5-log removal of Cryptosporidium surrogates (required from Guideline for Canadian Drinking Water Quality) can be achieved in the direct filtration during Edmonton cold-water condition when the pretreatment processes are optimized using 0.454 mg/L of alum as Al with addition of 0.5 mg/L poly DADMAC.
Water Research, 2019
The prevalence and seasonal variation of 7 viruses in 6 major rivers in Alberta were assessed usi... more The prevalence and seasonal variation of 7 viruses in 6 major rivers in Alberta were assessed using a combination of qPCR, cell culture and integrated cell culture with qPCR (ICC-qPCR). Water samples were collected monthly from rivers at different sites upstream and downstream of major urban centers. Seven viruses including rotavirus, adenovirus, astrovirus, norovirus, sapovirus, JC virus and enterovirus, were detected in at least one of the water samples at each site using qPCR. Rotavirus was most common with concentration ranging from 2.3 to 4.5 log 10 genomic equivalent (GE) copies/L. Norovirus, sapovirus, astrovirus, adenoviruses and JC virus peaked during the winter (November to March). Viruses were most prevalent at the Bow River sampling site downstream of the City of Calgary, followed by the North Saskatchewan River site downstream of the City of Edmonton and the Red Deer River site downstream of the City of Red Deer. The detection rates and quantity of viruses had significant difference in the sampling sites between upstream and downstream of major urban centers (p < 0.001). 14% of the samples tested positive using viral culture indicating the presence of infectious viruses in river. Sequencing analysis identified human rotavirus in 75% of the samples collected from downstream versus 37% of the samples collected from upstream sites (p < 0.02). Multivariate binary regression showed that human activity in watersheds is a significant determinant of viruses in Alberta's Rivers. The discharge from wastewater treatment plants may be the possible sources of viral contamination. Seasonal coincidence of acute viral gastroenteritis outbreaks and monthly peak occurrence of enteric viruses in river water implies potential impact of waterborne viruses on human health.
Proceedings of the Water Environment Federation, 2005
ABSTRACT
Proceedings of the Water Environment Federation, 2009
Journal of Applied Microbiology, 2015
Aims: To assess the removal of viruses through the multiple steps of wastewater treatment in a fu... more Aims: To assess the removal of viruses through the multiple steps of wastewater treatment in a full-scale municipal wastewater treatment plant in Alberta, Canada. Methods and Results: Samples were collected after each of the five treatment steps for a period of 16 months. The amount of viruses and their infectivity were analysed using real-time quantitative PCR (qPCR) and integrated viral cell culture (ICC), respectively. Bacterial indicator Escherichia coli was also tested using membrane filtration. Seven viruses including Norovirus (NoV), Rotavirus (RV), Sapovirus (SaV), Astrovirus (AsV), Adenovirus (AdV), Enterovirus (EV) and JC virus (JCV) were detected in 16 primary effluents in which infectious viruses were present. Different treatment steps showed various efficiencies in virus removal, with membrane ultrafiltration as the most effective at 4Á6-7Á0 log reduction. Conclusions: We observed high prevalence of viruses in raw wastewater and different viral reduction after various treatment steps. The discharge of treated wastewater with infectious viruses represents potential risks to human, animal and environmental health. Significance and Impact of the Study: This study provides a comprehensive assessment of the removal of NoV, RV, SaV, AsV, AdV, EV, JCV and Reovirus from wastewater by current procedures of municipal wastewater treatment and discusses the applicability of various viruses as viral indicators for water quality.
Canadian Journal of Civil Engineering, 2015
Predicting disinfectant concentrations in water distribution systems using water quality models r... more Predicting disinfectant concentrations in water distribution systems using water quality models requires the input of the wall decay coefficient of the disinfectant. In this study, field water sampling data was integrated with network hydraulic and water quality model simulations of a section of the municipal water distribution system in the City of Edmonton, composed of predominantly cast iron piping, to determine a wall decay coefficient for combined chlorine (chloramine). Unique combined chlorine wall decay coefficients that provided the best fit of model-predicted chlorine concentrations to the field data were determined at two temperatures. Using the determined wall decay coefficients, the water quality model can be used to predict combined chlorine concentrations.
Water Research, 2000
The effect of medium pressure ultraviolet radiation on Giardia muris was studied using a collimat... more The effect of medium pressure ultraviolet radiation on Giardia muris was studied using a collimated beam apparatus with filtered surface water from the Grand River, Kitchener, Ontario, Canada. UV doses ranged from 5 to 83 mJ/cm 2 and resulted in 23 log-units of reduction ...
Water Research, 2009
The action spectra of Bacillus subtilis spores (ATCC6633) and Salmonella typhimurium LT2 were cha... more The action spectra of Bacillus subtilis spores (ATCC6633) and Salmonella typhimurium LT2 were characterized using physical radiometry for irradiance measurements and a multiple target model to interpret the inactivation kinetics. The observed action spectrum of B. subtilis spores deviated significantly from the relative absorbance spectrum of the DNA purified from the spores, but matched quite well with the relative absorbance spectrum of decoated spores. The action spectrum of B. subtilis spores determined in this study was statistically different from those reported in previous studies. On the other hand, the action spectrum of S. typhimurium bacteria matched quite well with the relative absorbance spectrum of DNA extracted from vegetative cells, except in the region below 240 nm. It is concluded that the common use of the relative DNA absorbance spectrum as a surrogate for the germicidal action spectrum can result in systematic errors when evaluating the performance of a polychromatic UV light reactors using bioassays. For example, if the weighted germicidal fluence (UV dose) calculated using the relative DNA absorbance spectrum as the germicidal weighting factor is found to be 40 mJ cm À2 for a medium pressure lamp UV reactor, that calculated using the relative action spectrum of B. subtilis spores, as determined in this study, would be 66 mJ cm À2 .
Water Research, 2009
Several waterborne outbreaks of giardiasis have been linked to discharge of wastewater effluents ... more Several waterborne outbreaks of giardiasis have been linked to discharge of wastewater effluents into surface water. Little is known about the infectivity of Giardia lamblia cysts present in UV treated wastewater effluents. In this study, the infectivity of G. lamblia cysts, recovered from primary effluent and secondary effluent, both upstream and downstream of operating full-scale UV reactors at four wastewater treatment plants, was assessed using the Mongolian gerbil model. Infectivity of cysts obtained from the primary effluents was scored as either strong or moderate for induction of infection in gerbils at three out of four wastewater treatment plants. G. lamblia recovered from secondary effluent both upstream and downstream of the UV reactors caused weak infections in the gerbils. The probability of weak infections caused by inoculums of 50-1400 cysts per gerbil was, on the average, reduced by approximately 10% at the four wastewater UV installations with coliform reduction equivalent doses ranging from 6 to 18 mJ/cm 2. The UV systems provided considerably less inactivation of the parasite than expected based on the UV dose response of Giardia reported in the literature.
Water Research, 2003
Static mixers may be used to dissolve gaseous ozone in water treatment facilities in order to pro... more Static mixers may be used to dissolve gaseous ozone in water treatment facilities in order to provide protection against the waterborne parasite Cryptosporidium parvum. The objective of this study was to determine the effect of a brief exposure to turbulent gas-liquid mixing conditions in a static mixer on inactivation of C. parvum oocysts by ozone. Inactivation measured in an ozone contacting apparatus that employed a static mixer for ozone dissolution was compared to predictions based on a previously published kinetic model of C. parvum inactivation by dissolved ozone in gently stirred batch reactors. Although initial contact in the static mixer had no immediate effect on the oocysts, a 20% increase in the rate of inactivation during subsequent contact with dissolved ozone was observed. Increasing the degree of turbulence within the static mixer did not yield additional inactivation. Use of static mixers for dissolution of ozone in drinking water treatment systems may provide limited enhancement of C. parvum inactivation by dissolved ozone.
Ozone: Science & Engineering, 2005
The U.S. EPA is considering segregated flow analysis as an alternative calculation method to dete... more The U.S. EPA is considering segregated flow analysis as an alternative calculation method to determine Cryptosporidium parvum inactivation credit in continuous-flow ozone contactors in drinking water treatment facilities. A computer method is presented in which C. parvum inactivation in the reactive flow segment of a hypothetical ozone contactor with a predetermined residence time distribution is calculated based on the assumption of either completely segregated or completely micro-mixed flow. In a series of computer simulations using typical ozonation conditions in a water treatment facility, inactivation predicted assuming complete segregation was 0.3 to more than 2.0 log greater than that predicted assuming complete micro-mixing, depending on the level of back-mixing, ozone decomposition rate and inactivation level. CFSTR-in-series model predictions of inactivation were between those of segregated flow analysis and micro-mixed analysis. It was concluded that segregated flow analysis calculations may result in significant over-prediction of C. parvum inactivation credit in ozone contactors and should be used with caution.
Journal of Virological Methods, 2012
Practical pre-analytical and analytical procedures were developed and validated for detection of ... more Practical pre-analytical and analytical procedures were developed and validated for detection of enteric viruses in three water matrices. Both RNA viruses (norovirus, coxsackievirus, echovirus, and rotavirus) and DNA virus (adenovirus 41) were included in the study. The NanoCeram 90mm laminated disc with electropositive filter and procedures of filtration, elution and flocculation were utilized to concentrate known amount of viruses in different water matrices. Real time quantitative PCR was used to evaluate the recovery of virus and cell culture to assess viral infectivity. There was no PCR inhibition using various concentrations and pH of beef extract eluting buffer. A good recovery of the viruses spiked in 10L of deionized water was achieved for serial dilutions of coxsackievirus (41-67%), echovirus (22-90%), norovirus (23-44%) and rotavirus (24-46%). Relatively lower recovery was observed for adenovirus 41 (24-35%). There was no significant difference in viral recovery from deionized, tap and river water samples. The infectivity of recovered adenovirus, coxsackievirus and echovirus was demonstrated using in vitro cell culture. The pre-analytical and analytic procedures attained consistent recovery of RNA and DNA viruses both as infectious viral particles and viral genome, provided effective removal of inhibitory substances, achieved reliable reproducibility, and were relatively inexpensive for monitoring viruses in water.
Journal of Environmental Engineering and Science, 2007
A three-dimensional (3-D) computational fluid dynamic model that predicts the performance of a fu... more A three-dimensional (3-D) computational fluid dynamic model that predicts the performance of a full-scale medium-pressure lamp ultraviolet (UV) reactor for disinfection of drinking water is described. The model integrates velocity field, fluence rate distribution, and particle trajectory calculations with a microorganism inactivation kinetic model to arrive at predictions of reduction equivalent dose and microorganism inactivation for MS2 coliphage. A rational approach to determining an appropriate number of fluid particles that would generate the required computational precision is presented. Predictions of inactivation and equivalent dose were found to be sensitive to computational mesh geometry (hexahedral versus tetrahedral) but were less sensitive to the value of the Lagrangian empirical constant used in the random walk model and to choice of turbulence model (κ – εε versus Reynolds stress). Non-steady-state (dynamic) simulations produced results that were similar to those of s...
Environmental Technology, 1991
ABSTRACT
Journal of Environmental Engineering, 2014
AbstractThe drinking water industry is paying more attention to water quality monitoring systems ... more AbstractThe drinking water industry is paying more attention to water quality monitoring systems that provide real-time detection of contaminants in drinking water distribution systems. This thesis presents the results of an experimental challenge study on one such system, the Hach GuardianBlue Early Warning System. Contaminants of interest included organic and inorganic chemicals, and sewage. Experimental results showed that the system responded to all of the injected contaminants, except dichloromethane, but failed to correctly identify any of the contaminants. A mathematical model was used to determine the detection limit. Several system design and operational limitations were also identified. The GuardianBlue system could not identify a contaminant when it detected the changes in water quality parameters. A few improvements on the system design need to be done before the system can be deployed in the distribution network. At this moment, it can be merely used as an online water quality monitor.
BMJ Open
IntroductionThe COVID-19 pandemic has an excessive impact on residents in long-term care faciliti... more IntroductionThe COVID-19 pandemic has an excessive impact on residents in long-term care facilities (LTCF), causing high morbidity and mortality. Early detection of presymptomatic and asymptomatic COVID-19 cases supports the timely implementation of effective outbreak control measures but repetitive screening of residents and staff incurs costs and discomfort. Administration of vaccines is key to controlling the pandemic but the robustness and longevity of the antibody response, correlation of neutralising antibodies with commercial antibody assays, and the efficacy of current vaccines for emerging COVID-19 variants require further study. We propose to monitor SARS-CoV-2 in site-specific sewage as an early warning system for COVID-19 in LTCF and to study the immune response of the staff and residents in LTCF to COVID-19 vaccines.Methods and analysisThe study includes two parts: (1) detection and quantification of SARS-CoV-2 in LTCF site-specific sewage samples using a molecular assa...
Colloids and Surfaces B: Biointerfaces, 2019
Pilot-scale direct filtration challenge experiments were conducted to determine the impact of che... more Pilot-scale direct filtration challenge experiments were conducted to determine the impact of chemical pretreatment and filter design on the removal of Cryptosporidium surrogates dosed into the filter influent water at low temperatures (Average 0.5˚C). Copolymers-modified microspheres were identified as representative Cryptosporidium oocysts surrogates based on our previous findings and were used to evaluate the oocysts filtration removal at this pilot-scale study. The operational parameters examined included coagulant type (aluminum sulfate (alum) versus polyaluminium chloride (PACl)), filter aid polymer type (polyamine Magnafloc ® LT-7981 versus poly(Dimethyl Diallyl Ammonium Chloride) (polyDADMAC) Magnafloc ® LT-7995) and dose (0.5 versus 2.0 mg/L), and filter configuration (regular versus deep bed filters). The study found that higher Cryptosporidium surrogate removal was associated with higher polymer dose (2 mg/L) of polyDADMAC polymer and the deep bed filter configuration. The difference in surrogate removal between PACl and alum was no significant at cold temperature conditions tested. The deep bed filters were associated with higher surrogate removal, while exhibiting lower rates of flow reduction and longer filter run time. This work emphasizes the importance of optimizing chemical pretreatment and filter configuration for removing surrogates of Cryptosporidium oocysts in cold-water conditions in granular media water filtration processes. This pilot-scale study also demonstrated the exceed 2.5-log removal of Cryptosporidium surrogates (required from Guideline for Canadian Drinking Water Quality) can be achieved in the direct filtration during Edmonton cold-water condition when the pretreatment processes are optimized using 0.454 mg/L of alum as Al with addition of 0.5 mg/L poly DADMAC.
Water Research, 2019
The prevalence and seasonal variation of 7 viruses in 6 major rivers in Alberta were assessed usi... more The prevalence and seasonal variation of 7 viruses in 6 major rivers in Alberta were assessed using a combination of qPCR, cell culture and integrated cell culture with qPCR (ICC-qPCR). Water samples were collected monthly from rivers at different sites upstream and downstream of major urban centers. Seven viruses including rotavirus, adenovirus, astrovirus, norovirus, sapovirus, JC virus and enterovirus, were detected in at least one of the water samples at each site using qPCR. Rotavirus was most common with concentration ranging from 2.3 to 4.5 log 10 genomic equivalent (GE) copies/L. Norovirus, sapovirus, astrovirus, adenoviruses and JC virus peaked during the winter (November to March). Viruses were most prevalent at the Bow River sampling site downstream of the City of Calgary, followed by the North Saskatchewan River site downstream of the City of Edmonton and the Red Deer River site downstream of the City of Red Deer. The detection rates and quantity of viruses had significant difference in the sampling sites between upstream and downstream of major urban centers (p < 0.001). 14% of the samples tested positive using viral culture indicating the presence of infectious viruses in river. Sequencing analysis identified human rotavirus in 75% of the samples collected from downstream versus 37% of the samples collected from upstream sites (p < 0.02). Multivariate binary regression showed that human activity in watersheds is a significant determinant of viruses in Alberta's Rivers. The discharge from wastewater treatment plants may be the possible sources of viral contamination. Seasonal coincidence of acute viral gastroenteritis outbreaks and monthly peak occurrence of enteric viruses in river water implies potential impact of waterborne viruses on human health.
Proceedings of the Water Environment Federation, 2005
ABSTRACT
Proceedings of the Water Environment Federation, 2009
Journal of Applied Microbiology, 2015
Aims: To assess the removal of viruses through the multiple steps of wastewater treatment in a fu... more Aims: To assess the removal of viruses through the multiple steps of wastewater treatment in a full-scale municipal wastewater treatment plant in Alberta, Canada. Methods and Results: Samples were collected after each of the five treatment steps for a period of 16 months. The amount of viruses and their infectivity were analysed using real-time quantitative PCR (qPCR) and integrated viral cell culture (ICC), respectively. Bacterial indicator Escherichia coli was also tested using membrane filtration. Seven viruses including Norovirus (NoV), Rotavirus (RV), Sapovirus (SaV), Astrovirus (AsV), Adenovirus (AdV), Enterovirus (EV) and JC virus (JCV) were detected in 16 primary effluents in which infectious viruses were present. Different treatment steps showed various efficiencies in virus removal, with membrane ultrafiltration as the most effective at 4Á6-7Á0 log reduction. Conclusions: We observed high prevalence of viruses in raw wastewater and different viral reduction after various treatment steps. The discharge of treated wastewater with infectious viruses represents potential risks to human, animal and environmental health. Significance and Impact of the Study: This study provides a comprehensive assessment of the removal of NoV, RV, SaV, AsV, AdV, EV, JCV and Reovirus from wastewater by current procedures of municipal wastewater treatment and discusses the applicability of various viruses as viral indicators for water quality.
Canadian Journal of Civil Engineering, 2015
Predicting disinfectant concentrations in water distribution systems using water quality models r... more Predicting disinfectant concentrations in water distribution systems using water quality models requires the input of the wall decay coefficient of the disinfectant. In this study, field water sampling data was integrated with network hydraulic and water quality model simulations of a section of the municipal water distribution system in the City of Edmonton, composed of predominantly cast iron piping, to determine a wall decay coefficient for combined chlorine (chloramine). Unique combined chlorine wall decay coefficients that provided the best fit of model-predicted chlorine concentrations to the field data were determined at two temperatures. Using the determined wall decay coefficients, the water quality model can be used to predict combined chlorine concentrations.
Water Research, 2000
The effect of medium pressure ultraviolet radiation on Giardia muris was studied using a collimat... more The effect of medium pressure ultraviolet radiation on Giardia muris was studied using a collimated beam apparatus with filtered surface water from the Grand River, Kitchener, Ontario, Canada. UV doses ranged from 5 to 83 mJ/cm 2 and resulted in 23 log-units of reduction ...
Water Research, 2009
The action spectra of Bacillus subtilis spores (ATCC6633) and Salmonella typhimurium LT2 were cha... more The action spectra of Bacillus subtilis spores (ATCC6633) and Salmonella typhimurium LT2 were characterized using physical radiometry for irradiance measurements and a multiple target model to interpret the inactivation kinetics. The observed action spectrum of B. subtilis spores deviated significantly from the relative absorbance spectrum of the DNA purified from the spores, but matched quite well with the relative absorbance spectrum of decoated spores. The action spectrum of B. subtilis spores determined in this study was statistically different from those reported in previous studies. On the other hand, the action spectrum of S. typhimurium bacteria matched quite well with the relative absorbance spectrum of DNA extracted from vegetative cells, except in the region below 240 nm. It is concluded that the common use of the relative DNA absorbance spectrum as a surrogate for the germicidal action spectrum can result in systematic errors when evaluating the performance of a polychromatic UV light reactors using bioassays. For example, if the weighted germicidal fluence (UV dose) calculated using the relative DNA absorbance spectrum as the germicidal weighting factor is found to be 40 mJ cm À2 for a medium pressure lamp UV reactor, that calculated using the relative action spectrum of B. subtilis spores, as determined in this study, would be 66 mJ cm À2 .
Water Research, 2009
Several waterborne outbreaks of giardiasis have been linked to discharge of wastewater effluents ... more Several waterborne outbreaks of giardiasis have been linked to discharge of wastewater effluents into surface water. Little is known about the infectivity of Giardia lamblia cysts present in UV treated wastewater effluents. In this study, the infectivity of G. lamblia cysts, recovered from primary effluent and secondary effluent, both upstream and downstream of operating full-scale UV reactors at four wastewater treatment plants, was assessed using the Mongolian gerbil model. Infectivity of cysts obtained from the primary effluents was scored as either strong or moderate for induction of infection in gerbils at three out of four wastewater treatment plants. G. lamblia recovered from secondary effluent both upstream and downstream of the UV reactors caused weak infections in the gerbils. The probability of weak infections caused by inoculums of 50-1400 cysts per gerbil was, on the average, reduced by approximately 10% at the four wastewater UV installations with coliform reduction equivalent doses ranging from 6 to 18 mJ/cm 2. The UV systems provided considerably less inactivation of the parasite than expected based on the UV dose response of Giardia reported in the literature.
Water Research, 2003
Static mixers may be used to dissolve gaseous ozone in water treatment facilities in order to pro... more Static mixers may be used to dissolve gaseous ozone in water treatment facilities in order to provide protection against the waterborne parasite Cryptosporidium parvum. The objective of this study was to determine the effect of a brief exposure to turbulent gas-liquid mixing conditions in a static mixer on inactivation of C. parvum oocysts by ozone. Inactivation measured in an ozone contacting apparatus that employed a static mixer for ozone dissolution was compared to predictions based on a previously published kinetic model of C. parvum inactivation by dissolved ozone in gently stirred batch reactors. Although initial contact in the static mixer had no immediate effect on the oocysts, a 20% increase in the rate of inactivation during subsequent contact with dissolved ozone was observed. Increasing the degree of turbulence within the static mixer did not yield additional inactivation. Use of static mixers for dissolution of ozone in drinking water treatment systems may provide limited enhancement of C. parvum inactivation by dissolved ozone.
Ozone: Science & Engineering, 2005
The U.S. EPA is considering segregated flow analysis as an alternative calculation method to dete... more The U.S. EPA is considering segregated flow analysis as an alternative calculation method to determine Cryptosporidium parvum inactivation credit in continuous-flow ozone contactors in drinking water treatment facilities. A computer method is presented in which C. parvum inactivation in the reactive flow segment of a hypothetical ozone contactor with a predetermined residence time distribution is calculated based on the assumption of either completely segregated or completely micro-mixed flow. In a series of computer simulations using typical ozonation conditions in a water treatment facility, inactivation predicted assuming complete segregation was 0.3 to more than 2.0 log greater than that predicted assuming complete micro-mixing, depending on the level of back-mixing, ozone decomposition rate and inactivation level. CFSTR-in-series model predictions of inactivation were between those of segregated flow analysis and micro-mixed analysis. It was concluded that segregated flow analysis calculations may result in significant over-prediction of C. parvum inactivation credit in ozone contactors and should be used with caution.
Journal of Virological Methods, 2012
Practical pre-analytical and analytical procedures were developed and validated for detection of ... more Practical pre-analytical and analytical procedures were developed and validated for detection of enteric viruses in three water matrices. Both RNA viruses (norovirus, coxsackievirus, echovirus, and rotavirus) and DNA virus (adenovirus 41) were included in the study. The NanoCeram 90mm laminated disc with electropositive filter and procedures of filtration, elution and flocculation were utilized to concentrate known amount of viruses in different water matrices. Real time quantitative PCR was used to evaluate the recovery of virus and cell culture to assess viral infectivity. There was no PCR inhibition using various concentrations and pH of beef extract eluting buffer. A good recovery of the viruses spiked in 10L of deionized water was achieved for serial dilutions of coxsackievirus (41-67%), echovirus (22-90%), norovirus (23-44%) and rotavirus (24-46%). Relatively lower recovery was observed for adenovirus 41 (24-35%). There was no significant difference in viral recovery from deionized, tap and river water samples. The infectivity of recovered adenovirus, coxsackievirus and echovirus was demonstrated using in vitro cell culture. The pre-analytical and analytic procedures attained consistent recovery of RNA and DNA viruses both as infectious viral particles and viral genome, provided effective removal of inhibitory substances, achieved reliable reproducibility, and were relatively inexpensive for monitoring viruses in water.
Journal of Environmental Engineering and Science, 2007
A three-dimensional (3-D) computational fluid dynamic model that predicts the performance of a fu... more A three-dimensional (3-D) computational fluid dynamic model that predicts the performance of a full-scale medium-pressure lamp ultraviolet (UV) reactor for disinfection of drinking water is described. The model integrates velocity field, fluence rate distribution, and particle trajectory calculations with a microorganism inactivation kinetic model to arrive at predictions of reduction equivalent dose and microorganism inactivation for MS2 coliphage. A rational approach to determining an appropriate number of fluid particles that would generate the required computational precision is presented. Predictions of inactivation and equivalent dose were found to be sensitive to computational mesh geometry (hexahedral versus tetrahedral) but were less sensitive to the value of the Lagrangian empirical constant used in the random walk model and to choice of turbulence model (κ – εε versus Reynolds stress). Non-steady-state (dynamic) simulations produced results that were similar to those of s...
Environmental Technology, 1991
ABSTRACT
Journal of Environmental Engineering, 2014
AbstractThe drinking water industry is paying more attention to water quality monitoring systems ... more AbstractThe drinking water industry is paying more attention to water quality monitoring systems that provide real-time detection of contaminants in drinking water distribution systems. This thesis presents the results of an experimental challenge study on one such system, the Hach GuardianBlue Early Warning System. Contaminants of interest included organic and inorganic chemicals, and sewage. Experimental results showed that the system responded to all of the injected contaminants, except dichloromethane, but failed to correctly identify any of the contaminants. A mathematical model was used to determine the detection limit. Several system design and operational limitations were also identified. The GuardianBlue system could not identify a contaminant when it detected the changes in water quality parameters. A few improvements on the system design need to be done before the system can be deployed in the distribution network. At this moment, it can be merely used as an online water quality monitor.